Hidden Gibbons 
Enchantment
When an opponent casts an instant spell, if this permanent is an enchantment, it becomes a 4/4 Ape creature.
Legality
standardNOT LEGALpioneerNOT LEGALmodernNOT LEGALlegacyLEGALvintageLEGALcommanderLEGAL
Enchantment
When an opponent casts an instant spell, if this permanent is an enchantment, it becomes a 4/4 Ape creature.